T_e([O II]) as a function of T_e([O III]) for the model from Garnett (1992) (solid black line) in comparison with T_e([O II]) and T_e([O III]) derived for the SE knot in I Zw 18 (black circle). The solid blue line represents the quadratic model from Méndez-Delgado et al. (2023) for T_e([N II]) as a function of T_e([O III]), and the red and green lines represent the relations from Cataldi et al. (2025) and Pagel et al. (1992), respectively. For this model, we preserved a limited range of T_e([O III]), which represents the range of T_e([O III]) in its calibration sample.